1. Field of the Invention
The present invention relates to a temperature control apparatus, and particularly to a temperature control apparatus for controlling the temperature of an electronic device at the time of test.
2. Description of the Related Art
Prior to shipment, performance test of an electronic device, for example, a semiconductor chip needs to be carried out at a room temperature or a higher temperature or a lower temperature. When the performance test of a semiconductor chip is carried out at a room temperature under a rated current, heat is generated inside the semiconductor chip by this current so that the temperature of the chip is raised more than the room temperature. Thus, the semiconductor chip needs to be cooled appropriately to maintain the temperature at the room temperature. When the semiconductor chip is heated with a heater or the like in case of high temperature test, it needs to be cooled appropriately in order to prevent the temperature from being raised more than a setting temperature. These cases of cooling are carried out with a temperature setting head loaded with a semiconductor chip connected to a predetermined cooling system.
As a conventional temperature control apparatus, a temperature control apparatus disclosed in, for example, U.S. Pat. No. 6,668,570 has been known. This conventional apparatus, as shown in FIG. 1 of this patent document, executes temperature control of an electronic device 10 by a thermal head 14 which combines a passage 36 in which refrigerant flows with an electric heater 30 in contact with the electronic device 10. In a cooling system using the thermal head 14 having such a structure, heat is generated from the electronic device 10 and the heater 30 and this heat is absorbed by the cooling system. Therefore, when the amount of heat generated from the thermal head increases at the time of high temperature test, for example, the quantity of heat absorbed by refrigerant in the thermal head 14 increases so that the temperature of refrigerant supplied to a compressor 32 rises. As a result, the temperature in the compressor 32 is raised by heat generated therein when refrigerant is compressed and if this temperature exceeds a setting maximum temperature of the compressor 32, a large thermal stress is applied to components inside the compressor 32, so that the compressor 32 may be possibly damaged. Therefore, the quantity of heat generated from the heater 14 needs to be controlled strictly in order to prevent this serious phenomenon. This leads to increase in cost of the entire temperature control apparatus and a temperature controllable range between the lower limit and upper limit of the temperature control narrows, thereby limiting an electronic device which can be tested to particular ones.